Explorer Bertrand Piccard explains why he's aiming to carry out an unprecedented mission: to circle the planet in a solar-powered airplane. Ford Executive Chairman Bill Ford describes how we can create a green future of smart roads and smart cars. Zipcar co-founder Robin Chase makes the case for car-sharing as the solution to global gridlock. Former New York City Transportation Commissioner Janette Sadik-Khan says cities can tackle the challenges of tomorrow by completely re-imagining our streets today. Entrepreneur Richard Branson shares his vision for private, commercial space travel. Learn more or listen again to this week's show. Banner image: iStockphoto